There is currently a significant need for accurate on-board weighing systems for certain vehicles like tractor-trailer combinations which have dual axles. The weighing of tractor-trailer loads, for instance, is now typically done at roadside weighing stations. The weighing process may take considerable time and large fines may be levied if the vehicle is significantly overweight, even unknowingly. An accurate vehicle on-board weighing system would reduce significantly the uncertainty of the actual weight of the vehicle load and thus reduce or eliminate fines due to overweight loads. The vehicle may also be confidently loaded close to the legal limit with the aid of an on-board system. Further, a continuing accurate knowledge of load weight is attained by use of an accurate on-board system.
As mentioned above, however, most tractor-trailer vehicles do not have an on-board weighing system, primarily because the use of an on-board weighing system for such vehicles has heretofore required rather elaborate modifications to the vehicle. In such an on-board system, load cells are typically installed between a portion of the suspension system of the vehicle and the frame. However, in order not to increase the overall height of the vehicle, i.e. the trailer of a tractor-trailer combination, a portion of the frame must be cut out and the load cell welded in place. A portion of the load-equalizing part of the suspension system, i.e. the equalizer hanger, is fixed to the load cell and the equalizer box itself is then attached to the hanger.
Obviously, such modifications to new vehicles are costly and retrofitting an existing vehicle is even more expensive. Replacement of welded-in load cells is of course quite difficult and expensive as well. Also, there are frequently problems with the accuracy of such devices, due to horizontal loads on the load cell caused by the particular physical arrangement of the load cell relative to the trailer.
The present invention incorporates a completely different structural approach to the use of load cells on such vehicles in order to produce accurate, reliable load measurements. The present invention also requires no modification to the frame of the vehicle.